In the treatment of webs of material and particularly the treatment of fabrics, it is a common practice to subject the fabric to treatment with a liquid and to then withdraw the liquid from the fabric under suction prior to drying by heating or other processes.
For example, a textile web may be treated with an organic solvent, e.g. as part of a dyeing or other textile-finishing operation, whereupon the major part of the solvent is removed from the web by passing the same over a surface having an opening which is evacuated. The fabric may thereafter be subjected to heating or the like to volatilize any residual solvent.
In a textile-treating apparatus which utilizes suction to recover at least a portion of the liquid used to treat the fabric, it is conventional to pass the web across a longitudinally extending slot of an evacuated tube so that the liquid is drawn into the tube through this slot. It is with such devices that the present invention is concerned.
German open application (Offenlegungsschrift) DT-OS 24 55 194 discloses a system of this type in which the width of the gap or slot is adjustable to control the suction applied to the web.
In this arrangement, the slot or gap is provided between two tube or shell halves which define the slot as a gap between them. The gap width is adjustable by pins extending transverse to the tube axis and movable to draw the shell halves together or urge them apart. The pins are actuated from a remote location by means of a worm gear and spindle.
The pins, however, lie within the duct formed by the tube halves and which is evacuated so that contaminants such as slubbing, filaments, fleece or the like can accumulate upon or around the pin and give rise to blockage of the duct. A pin within the duct also creates problems in the cleaning of the latter and may even interfere with the suction which can be developed at the gap or slot.